\documentclass{article}
\usepackage[x11names, rgb]{xcolor}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{snakes,arrows,shapes}
\usepackage{amsmath}
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\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{0pt}%
\usetikzlibrary{automata}%

\begin{document}
\pagestyle{empty}
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\enlargethispage{100cm}
% Start of code
\begin{tikzpicture}[>=latex',join=bevel,]
\tikzstyle{every state}=[draw=blue!50,very thick,fill=blue!20]%
\node (q0) at (264bp,546bp) [state] {$\{q_{5}\}$};
  \node (q3) at (123bp,282bp) [state] {$\{q_{2}\}$};
  \node (q7) at (123bp,194bp) [state] {$\{q_{3}\}$};
  \node (q6) at (98bp,370bp) [state] {$\{q_{7}\}$};
  \node (q2) at (204bp,370bp) [state] {$\{q_{1}\}$};
  \node (q5) at (52bp,18bp) [state] {$\{q_{8}\}$};
  \node (q1) at (141bp,458bp) [state] {$\{q_{6},q_{0}\}$};
  \node (q4) at (123bp,106bp) [state] {$\{q_{4}\}$};
  \draw [->] (q3) ..controls (123bp,252bp) and (123bp,236bp)  .. node[auto] {$\overline{auctionRegistrationService#process}$} (q7);
  \draw [->] (q0) ..controls (225bp,518bp) and (191bp,494bp)  .. node[auto] {$\overline{seller#answer}$} (q1);
  \draw [->] (q7) ..controls (123bp,164bp) and (123bp,148bp)  .. node[auto] {$auctionRegistrationService#answer$} (q4);
  \draw [->] (q6) ..controls (96bp,342bp) and (96bp,329bp)  .. (99bp,318bp) .. controls (100bp,314bp) and (102bp,310bp)  .. node[auto] {$buyer#submit$} (q3);
  \draw [->] (q2) ..controls (199bp,341bp) and (194bp,327bp)  .. (186bp,318bp) .. controls (178bp,309bp) and (167bp,301bp)  .. node[auto] {$seller#submit$} (q3);
  \draw [->] (q5) ..controls (31bp,52bp) and (18bp,80bp)  .. (18bp,106bp) .. controls (18bp,370bp) and (18bp,370bp)  .. (18bp,370bp) .. controls (18bp,424bp) and (58bp,431bp)  .. node[auto] {$\overline{buyer#answer}$} (q1);
  \draw [->] (q1) ..controls (113bp,439bp) and (105bp,431bp)  .. (100bp,422bp) .. controls (96bp,415bp) and (95bp,406bp)  .. node[auto] {$seller#submit$} (q6);
  \draw [->] (q1) ..controls (170bp,439bp) and (180bp,431bp)  .. (186bp,422bp) .. controls (192bp,415bp) and (195bp,406bp)  .. node[auto] {$buyer#submit$} (q2);
  \draw [->] (q4) ..controls (99bp,77bp) and (83bp,57bp)  .. node[auto] {$\overline{seller#answer}$} (q5);
  \draw [->] (q4) ..controls (200bp,109bp) and (305bp,117bp)  .. (331bp,142bp) .. controls (348bp,158bp) and (343bp,170bp)  .. (343bp,194bp) .. controls (343bp,458bp) and (343bp,458bp)  .. (343bp,458bp) .. controls (343bp,488bp) and (317bp,513bp)  .. node[auto] {$\overline{buyer#answer}$} (q0);
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\end{tikzpicture}
% End of code

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\end{document}
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